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work connectivity. For these purposes, all rooop terminals operate at 250 mW. We developed two types of rooop terminals: standalone rooop terminals powered by solar batteries, which can operate on the top of buildings where no high-voltage public outlet is available and in times of natural disasters, and simple rooop terminals that can be installed easily in places where high-voltage public outlets are available. e standalone rooop terminal and the simple rooop terminal are shown in Fig. 3 (a) and (b), respectively.A standalone rooop terminal is powered by a solar cell system with a maximum capacity of 640 Wh, and the communication device attached to the terminal consumes approximately 2 W of power. e number of hours the terminal can operate continuously can be calculated using the following equation, assuming that the solar cell system is charged to 80%.640 Wh×80% / 2 W = 256 h(4)is result indicates that the communication device is capable of continuous operation for more than 10 days so that it can operate stably even under adverse weather conditions, such as during a rainy season. On one hand, the standalone rooop terminal is equipped with two separate antennas for data transmission and reception. On the other hand, the simple rooop terminal is equipped with only a single antenna capable of both data transmis-sion and reception for easier installation. Rooop terminals are capable of communicating with each other and receiv-ing bus GPS data and sensor data transmitted from the sensor terminals described in the next section. e rooop terminals are also equipped with a built-in GPS receiver.3.3Sensor terminalA sensor terminal (Sen) is equipped with temperature, humidity, brightness and motion sensors and a GPS receiver. Like the standalone rooop terminal, we also attached a solar cell system to the sensor terminal in order to make it operable at many outdoor locations. An example of a sensor terminal mounted on a vending machine is shown in Fig. 4. A sensor terminal operates at 20 mW and transmits data collected by its sensors to rooop terminals and communica-tion devices in buses entering communication range. We designed the sensor terminals to be capable of only data transmission and not reception to make them energy ecient.We also developed portable terminals for use in various demonstration experiments. However, we installed them in our testbeds only temporarily. erefore, we omitted them in this paper.Brightness sensorMotion sensorGPSTemperature/humidity sensor(in the base unit)CommunicationDevice(in the base unit)FiF4　Example of a sensor terminal mounted on a vending machineTransmission antennaCommunication deviceSolar cell panelSolar cell batteryReception antennaTransmission & reception antennaCommunication device(a)　Standalone rooftop terminal(b)　Simple rooftop terminalFiF3　Examples of installed rooftop terminals472-7 Development and Field Trial of D2D Networks for Local Area Information Collection and Distribution